Development of Mitochondria-Targeted PARP Inhibitors

Area of Science:

• Oncology
• Medicinal Chemistry
• Mitochondrial Biology

Background:

• Poly(ADP-ribose) polymerase (PARP) inhibitors are established anticancer drugs targeting homologous recombination-deficient (HRD) tumors.
• Targeting mitochondria for organelle-specific drug action remains a challenge.
• Developing mitochondria-targeted PARP inhibitors could improve efficacy and overcome resistance in HRD cancers.

Purpose of the Study:

• To design and synthesize novel mitochondria-targeted PARP inhibitors.
• To evaluate their ability to selectively accumulate in mitochondria and modulate PARP activity.
• To assess their anticancer efficacy and selectivity.

Main Methods:

• Synthesis of trialkyl(aryl)phosphonium conjugates of olaparib and rucaparib.
• Evaluation of PARP1 inhibition, cardiolipin binding affinity, and cytotoxicity in BRCA1-deficient breast cancer cells (HCC1937) and non-malignant cardiomyocytes (H9C2).

Main Results:

• Conjugates retained potent PARP1 inhibition (IC50 = 3.4-17 nM).
• Specific derivatives (2d, 6c) showed strong cardiolipin binding and enhanced cytotoxicity in HCC1937 cells (IC50 = 0.93, 2.01 µM), outperforming parent drugs.
• Reduced cytotoxicity in H9C2 cells indicated a favorable selectivity profile.

Conclusions:

• Phosphonium conjugation successfully confers mitochondrial targeting to PARP inhibitors.
• Mitochondria-targeted PARP inhibitors demonstrate enhanced anticancer potency and selectivity.
• This strategy holds promise for next-generation therapeutics against HR-deficient tumors, potentially improving efficacy and overcoming resistance.